Visual and magnetic recording systems

ABSTRACT

Disclosed is a system for visually and magnetically recording data indicative of characters on opposite sides of a paper sheet having a magnetizable backing. The data are recorded with a typewriter which includes a head for recording coded magnetic bits indicative of each character visually printed on the sheet. The head is coreless and is comprised of a plurality of windings, only certain of the windings write or record bipolarity magnetic bits onto the backing, the remaining windings serve as both spacer and erase windings. Recording is accomplished by feeding large amplitude, short duration current pulses to the recording windings. The magnetic bits for each magnetically recorded character are selectively erased by applying bipolarity, low duty-cycle pulses of successively lower amplitudes to the backing by way of the windings and different modes of erasing various areas on the recording medium are disclosed. Also disclosed is a system for decoding the magnetic bits stored on the backing, wherein a head sequentially scans a rotating line of magnetic bits and sequentially reads out each character of the line. The entire document is read by stepping the head from line to line.

United States Patent [191 Andreaggi et al.

[4 1 Oct. 7, 1975 [54] VISUAL AND MAGNETIC RECORDING SYSTEMS [75]Inventors: Joseph R. Andreaggi, Short Hills;

Robert J. Graf, Newark; Matthew J. Relis, Teaneck, all of NJ.

[73] Assignee: Joseph R. Andreaggi, Short Hills,

22 Filed: Dec. 28, 1973 21 Appl. No.: 429,206

Related U.S. Application Data [62] Division of Ser. No. 250,872, May 8,1972, Pat. No.

Primary Examiner\/incent P. Canney Attorney, Agent, or Firm lerry M.Presson 5 7 ABSTRACT Disclosed is a system for visually and magneticallyrecording data indicative of characters on opposite sides of a papersheet having a magnetizable backing. The data are recorded with atypewriter which includes a head for recording coded magnetic bitsindicative of each character visually printed on the sheet. The head iscoreless and is comprised of a plurality of windings, only certain ofthe windings write or record bipolarity magnetic bits onto the backing,the remaining windings serve as both spacer and erase windings.Recording is accomplished by feeding large amplitude, short durationcurrent pulses to the recording windings. The magnetic bits for eachmagnetically recorded character are selectively erased by applyingbipolarity, low duty-cycle pulses of successively lower amplitudes tothe backing by way of the windings and different modes of erasingvarious areas on the recording medium are disclosed. Also disclosed is asystem for decoding the magnetic bits stored on the backing, wherein ahead sequentially scans a rotating line of magnetic bits andsequentially reads out each character of the line. The entire documentis read by stepping the head from line to line.

7 Claims, 19 Drawing Figures r2 (FIGS.

Sheet 1 0f12 Oct. 7 ,1975

U.S. Patent US. Patent Oct. 7,1975 Sheet 2 of 12 3,911,481

RECORD/N6 aumvmr k k k k PULSES V V V WAVEFORMS M NE o 0 0 /v a/rs VOLT146 E WA 1/5 F ORMS U.S Patsm 0017,1975 Sheet 3 0f 12 3,911,481

US. Patent Oct. 7,1975 Sheet4 of 12 Sheet 5 0f 12 US. Patnt Oct. 7,1975

US. Patent 0017,1975 Sheet6 of 12 3,911,481

E RASE OURRE N T (FIG. /4)

SOURGE OF I. II- llllllll ll.

RECORD 8 US. Patent 061. 7,1975 shw 7 0f 12 3,911,481

ERASE CURRENT (FIE/4) cool/v6 1 m TRIX SOURCES OF RECORD/N6 ERASEWIND/N65 HAW/V6 RECORDINGS 53-! T053 '8 INTERLEAVED THEREBETWEEN US.Patent Oct. 7,1975 Sheet 8 of 12 3,911,481

US. Patent 0a. 7,1975 Sheet 10 of 12 3,911,481

VISUAL AND MAGNETIC RECORDING SYSTEMS This is a division of applicationSer. No. 250,872, filed May 8, 1972, now US. Pat. No. 3,823,405.

The present invention relates generally to systems for providing avisual and a corresponding magnetically encoded record of data and moreparticularly a system wherein the recorded data is stored on a singlemedium in both visual and magnetic modes with fixed positionalcorrelation therebetween.

Prior art systems of the type presently under consideration typicallyemploy permanent magnets mounted on type bars of a typewriter, thepermanent magnets being located either within or below the print font.In these systems, the magnetic data is recorded coincidentally as visualdata is typed on an opaque paper sheet having a magnetic backing thereonor impregnated with magnetic material. When a key of the typewriter isstruck, by an operators finger, permanent magnets are translated intocontact with, or in close proximity to, the magnetic portion of thesheet thereby generating magnetic flux on the surface of the sheet beingimprinted. Paper thickness and magnetic characteristics preventeffective recording through a paper sheet to a magnetic backing recordwith permanent magnets that strike the sheet from the paper or frontside. Hence, those system wherein magnetic data is recorded by relyingupon magnetic flux being transmitted through a sheet of paper to amagnetic backing are most likely not sufficient to enable detection ofthe magnetically recorded data without appreciable error. While errorsmay not be introduced by recording on a sheet of paper having magneticmaterial, such ferro magnetic particles, impregnated therein, such asheet generally takes on the dark hue of the black particles embeddedtherein making it difficult to discern the data visually recordedthereon. Also, erasure of typed material from paper having magneticmaterial embedded therein is impractical because of adverse effects onthe appearance of the printed material on the sheet and irregularitieslikely to be introduced by erasing on the magnetic surface. Suchirregularities may cause problems in correctly detecting recordedmagnetic flux during read-back.

Another disadvantage of systems wherein permanent magnets are carried onthe faces of type bars is that codes for space, tab or carriage returnfunctions cannot be included without providing special type bars on thetypewriter. Without tab or carriage return codes being introduced ontothe magnetic medium, the time required for reading out information fromthe magnetic record is considerably increased over the time required forrecords that carry such information. If no space code is provided on therecording medium, it is essential that the medium carry some suitabletype of timing or synchronizing tracks, in which case the recorded datacannot be considered as self-clocking or selfsynchronized.

Another disadvantage of systems employing permanent magnets on type barfaces is that the magnet flux level decreases in response to eachmechanical strike against a platen. Eventually, the magentic flux levelin the magnets could quite conceivably be reduced to a point wheresufficient magnetic flux is not recorded on the magnetic medium andaccurate reproduction of data during read-back does not occur. Whilemagnets may be recharged through the utilization of special equipment,the recharging operation is a costly and time-consuming operation. Inaddition, an operator is not usually apprised as to when recharging isnecessary.

In certain prior art systems permanent magnets are carried within thecharacter head itself. These systems, in addition to suffering from thepreviously discussed disadvantages, are likely to have the characterhead structure so weakened mechanically that a head might be brokenafter little use. Another disadvantage attendant with systems whereinmagnets are mounted on the head is that small characters, such as commasand periods, cannot carry the magnets because there is not enoughsurface area on the character head for more than one magnet. Inconsequence, a character such as a period or comma that is alwayslocated in the lower center portion of the key face cannot bedistinguished if a permanent magnet is embedded in the character itself.

Systems wherein permanent magnets are placed beneath the print characterhead are beset by additional problems. In general, only upper case printfonts can be utilized in such systems because the lower case characteris usually replaced with a magnet structure. While some systems proposedhave both upper and lower case fonts, with two magnets extending belowthe characters, it is believed that these systems are not practicalbecause different typewriters have different sized platens and platensfrequently become so out-of-round after any extended period of use. Theproblems of platen size and out-of-roundness are also prevalent with thesystems wherein a magnet replaces a lower case character because themagnet and the upper case character must both simultaneously strike arounded portion of the platen.

Another problem associated with having a magnet below the printcharacter is that the magnetically recorded data may not properly bewritten onto the magnetic medium at the bottom of the page. As is wellknown, typing personnel frequently are not aware of the fact that theyare typing on the last line of a sheet of paper, or type below a pointwhere the paper stays horizontally aligned with the result thatmagnetically recorded data below the line becomes difficult to detectaccurately. The possibility of incomplete erasures of erroneous magneticbits isalso likely in these systerns.

In a second class of prior art systems, electric signals are generatedin response to the activation of each key on a typewriter keyboard, withdifferent codes representing each key. In response to the electricsignals, different discrete areas or spots on a magnetic recordingmember are magnetized at a plurality of horizontal and vertical matrixpositions having a total area equal approximately to the area requiredfor a character. Because a plurality of horizontal parallel lines areutilized to represent each character magnetically, a single head is notfeasible for reading back all of the data associated with a particularcharacter. Moreover, because the number of magnetic spots recorded foreach character is variable and the spots are at different positions, therecord formed with these systems is not selfclocking and hencesynchronizing tracks must be provided.

In addition to the aforementioned problems, this system typicallysuffers from a lack of complete keyboard encoding functions, such asspacing, carriage return, shifting between upper and lower case andcharacter deletion.

The aforementioned disadvantages of known prior art systems areessentially overcome by the system of the instant invention. The instantsystem utilizes a single, flexible recording medium, to record in thevisually readable and magnetic modes. More specifically, the medium isconstituted of a paper sheet of suitable color, such as white, having aportion of one surface covered with a thin, ferromagnetic film or strip.In response to each key activation of an encoding typewriter,bi-polarity magnetic data bits are applied to discrete surface areas ofthe magnetic film. The magnetic data representative of each character isapplied to the magnetic film by means of a coreless magnetic recordinghead formed of a plurality of conductors. Each conductor is selectivelypulsed by a current in accordance with a code representative of theselected and depressed key. In one particular embodiment, eight bits arerecorded for each character of functional operation (e.g., space baractivation). Included are shift key and parity bits, whereby both lowerand upper case characters may be inscribed on and read from the recordand self-clocking can be realized. By applying bi-polarity data to themagnetic record the same number of bits is recorded for each character.By applying this data to the record serially, monotracks of data areobtained which represent serial character and functional key selectionsand activations, and therefore the record is completely self-clockingand no synchronizing track is required.

The magnetic recording head is positioned above and behind the locationwhere a type bar comes into contact with a sheet on the platen and theconductor of the recording head are preferably in direct contact withthe surface of the magnetizable film to achieve optimum flux-couplingbetween current-carrying conductors of this head and the magneticrecording medium. By positioning the recording head above the pointwhere the type bar contacts the sheet the problem of run-off of datamagnetically recorded at the bottom of the page is obviated. The problemof run-off at the top of the sheet normally does not arise because anoperator normally allows enough spacing or heading at the top of eachpage to permit contact between the recording head and the magnetizablefilm.

A magnetic recording head constructed in accordance with the presentinvention comprises a plurality of conductors, having extremely smallcross-sectional areas, positioned to contact the magnetic recordingmedium. In a typical recording head, 36 conductors are provided, witheight of the conductors supplying flux to the record and the remainingconductors serving as spacers between the flux-supplying conductors. Inone embodiment, the conductors comprise a plurality of single turnwires, whereas in a second embodiment the conductors take the form ofextremely thin strips. In both embodiments, the several conductors haveparallel longitudinal displaced axes. The conductors are topologicallyarranged so that the magnetic flux recorded thereby never exceeds thespace required for the largest character typed by non-proportionaltypewriters.

To enable sufficient bi-polarity magnetic flux to be imparted by theconductors to the magnetic medium, the conductors are pulsed withcurrents having an extremely large peak amplitude and a short enoughduration to prevent the conductors from being destroyed. We have foundthat current pulses having approximately 20 amperes peak value and 30microsecond duration impart sufficient flux to the record to enableaccurate results to be attained. The circuit utilized for generatingthese pulses comprises essentially a capacitor and a switch, such as asilicon-controlled rectifier. Charge stored on the capacitor is dumpedthrough the siliconcontrolled rectifier when a gate electrode of therectifier is activated.

It is, accordingly, an object of the present invention to provide a newand improved medium embodying human readable alphanumeric and magneticdata in fixed relative positional relationships and a system forencoding such data on the medium.

An additional object of the present invention is to provide a new andimproved system for recording human readable alphanumeric visual andmagnetic data on a single flexible sheet wherein coded signals derivedin response to a key being activated cause bipolarity magnetic signalsto be recorded on the sheet.

A further object of the present invention is to provide a new andimproved medium carrying human readable and magnetically recorded data,wherein the magnetically recorded data are self-clocking, and a systemfor recording such data on the medium.

Another object of the present invention is to provide a system forrecording human readable visual and magnetic data on a single sheet in a1:1 positional relationship, wherein problems associated with platensize and out-ofroundness are obviated.

An additional object of the invention is to provide a system for typinghuman readable visual characters and for recording magnetic data on apaper sheet having a magnetic backing, wherein magnetic flux is applieddirectly to the backing without being transmitted through the paper.

Still another object of the present invention is to provide a humanreadable visual and magnetic recording system wherein monotracks ofmagnetically recorded data are accurately spaced from correspondingmonotracks of the visually readable data.

Still a further object of the present invention is to provide a new andimproved system for recording human readable visual and magnetic data in1:1 positional relationship on a single sheet wherein the necessity forthe use of permanent magnets is obviated.

Yet another object of the present invention is to provide a new andimproved magnetic recording head capable of bit packing densities on theorder of bits per inch with static in situ recording and erasingcapabilities.

Still another object of the present invention is to provide a corelessrecord head for recording magnetic bits on a magnetic medium.

A further object of the invention is to provide a sheet carrying humanreadable and magnetic data in single spaced line relationship of upperand lower case alphanumeric characters, and to a system for recordingsame.

A further feature of the present invention relates to the apparatusemployed for selectively erasing magnetically recorded data from therecord. In prior art systems for recording visual and magnetic data in aprescribed, fixed positiona] relationship wherein erasing is proposed,it is accomplished by saturating the magnetic medium.

In accordance with the present invention, erasing of themedium isaccomplished by degaussing. In degaussing, the magnetic flux of theerased area is reduced below a detectable level for read-back purposes.This is accomplished by feeding a multiplicity of low duty cyclebi-polarity pulses to the record head. The first pulse in themultiplicity has a relatively high amplitude and succeeding pulsesdecrease successively in amplitude. In this manner the magnetic fluxlevel on the area of the magnetic record beneath the head issuccessively reduced, eventually to a level where the read circuitcannot discern a polarized magnetic bit in the area of erasure.

In accordance with another aspect of the erasing apparatus utilized inthe present invention, all of the conductors in the head assembly areconnected to be responsive to the erasing pulses. Thus, if perfectalignment between the paper and the write head is not maintained, as islikely to occur when a sheet is removed from a typewriter and thenre-inserted, previously recorded bits for a particular character areusually erased.

It is accordingly, still another object of the present invention toprovide a new and improved system for selectively erasing magneticallyrecorded characters on a sheet including visual and magnetic data in aprescribed, fixed positional relationship.

Yet still another object of the present invention is to provide a newand improved circuit particularly adapted for degaussing magneticrecords with large amplitude current pulses feeding extremely smallcrosssectional area conductors.

Still another feature of the present invention relates to a system forreading the recorded data. The recorded data are read bit by bit insequence as the magnetized backing rotates continuously past a negneticreading head. The entire record is read by indexing the reading headfrom one line to the next of the rotating record.

In consequence, yet a further object of the present invention is toprovide a new and improved system for reading magnetically recordeddata.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of several specific embodiments thereof,especially when taken in conjunction with the accompanying drawings,wherein:

FIG. I is a perspective view illustrating the position of the recordinghead of the present invention relative to a platen and sheet of paper onwhich human readable and magnetic data are written, the upper left handportion of the sheet being folded to depict magnetic bits appliedthereto by the recording heat in direct correspondence to the characterstyped on the front of the paper sheet.

FIG. 2 is a cross-sectional view taken along lines 2-2 of FIG. 1 of thecomposite sheet of paper and a flexible magnetizable backing integraltherewith, and additionally depicts typical electrical current waveformsfor writing bipolarity magnetic bits onto the magnetizable backing.

FIG. 3 is a cross-sectional view of the composite paper sheet andmagnetizable backing taken along the direction of recording andadditionally depicts voltage waveforms derived when the flux patternsfrom the backing are read.

FIG. 4 is a perspective view, in combination with a circuit blockdiagram, of one embodiment of a typewriter-encoder constructed inaccordance with the present invention.

FIG. 5 is a sectional view taken through the lines 5-5, FIG. 4, showingthe relationship between the magnetic recording head of the presentinvention in combination with other parts of the typewriter mechanism.

FIG. 6 is an enlarged, perspective view of a portion of a recording headframe and flux-producing windings constructed in accordance with thepresent invention.

FIG. 7 is a perspective view illustrating a system for vacuum drawingthe magnetizable backing into contact with the windings of the recordinghead.

FIG. 8 is a perspective view of a modification of a magnetic recordinghead wherein thin, metal strips are utilized as recording conductors.

FIG. 8A illustrates a typical arrangement of the interconnected metalstrips to provide a recording section for the recording head.

FIG. 9 is a perspective view illustrating a magnetic recording head ofthe type illustrated by FIG. 7 utilized in conjunction with aconventional typewriter having a ball-type printing element. 1

FIG. 10 illustrates a system for magnetically erasing discrete areasimmediately preceding or following a discrete area on which a magneticrecording is to be made.

FIG. 11 illustrates a system for supplying recording current to therecording head and for manually initiating magnetic erasure of discretemagnetizable areas immediately prior to recording on such areas.

FIG. 12 illustrates a system for automatically initiating magneticerasure of discrete magnetizable areas immediately prior to recording onsuch areas.

FIG. 13 is one embodiment of a circuit diagram for producing andsupplying recording currents to the recording head to produce magneticbits on the magnetizable backing.

FIG. 14 is a schematic diagram of a source of erase currents for thesystems of FIG. 10l2, inclusive.

FIG. 15 is a perspective view of one embodiment of a reading apparatusconstructed in accordance with the present invention.

FIG. 16 is a sectional view taken along lines l6-l6 of FIG. 15,illustrating the apparatus for maintaining a sheet in situ on the readhead of FIG. 15.

FIG. 17 is an enlarged view of mechanism for indexing the read head fromline-to-line in the embodiment of FIG. 15; and

FIG. 18 is a block diagram of circuitry for reading or printing outinformation received and decoded from the reading apparatus of FIG. 15.

THE VISUAL AND MAGNETIC RECORDING MEDIUM Before proceeding with thedetailed description of the apparatus of the present invention, atypical illustration of the data recorded by this apparatus may be hadby reference to FIGS. 1 and 2. In these figures, there is illustrated asheet of conventional bond paper 21 having a thickness on the order of 2to 3 mils and a flexible backing sheet, coating, film or layer 22composed of a highly magnetizable material, such as Fe- O or Fe O uponwhich magnetic data bits can be recorded and stored. The layer 22typically has a thickness on the order of 0.5 mil, and may be applied tothe entire surface of one side of the paper sheet 21 by conventionalmethods.

Printed on paper sheet 21 are conventional typewritten alphanumericcharacters, FIG. 1, each of which requires essentially the same discretesurface area. Typical conventional typewriters are designed to print lcharacters per inch with each line spaced approximately 0.16 inch apart.On this exemplary basis, each discrete area alloted to, and occupied by,an alphanumeric character has a width dimension of approximately 100mils and a height dimension of approximately 160 mils. Both upper andlower case letters of a complete SO-key typewriter keyboard can beprinted on sheet 21 in single spaced line relationship, if desired.Human readable characters on the same line can be imprinted insuccession and adjacent to each other on sheet 21, as in accordance withprinting normally associated with and obtainable from a conventionaltypewriter.

As may be seen from FIG. I, in vertical alignment with each alphanumericcharacter printed on sheet 21, there is a particular combination ofeight bits of bipolarity magnetic data properly coded to represent anysingle key on the typewriter keyboard. The data bits are depicted asshort vertical lines which together form a single track of magnetic bitson layer 22. An exemplary combination of eight bits is illustrated inFIG. 1. The area encompassing the eight bits is approximately the samewidth a typewritten character. Similarly, since these eight bits are thebinary-coded representation of one particular character, the height ofeach of the eight bits is approximately the same as that of thecharacter. Each group of eight bits is recorded simultaneously (or insitu) on the magnetic layer 22 in response to a corresponding keyactuation at a position slightly above the corresponding keycharacterization, whereby a prescribed, fixed or one-to-one positionalrelationship is provided, between a generated character line and acorresponding multibit magnetic data track comprised of a succession ofeightbit groups. Hence, in FIG. 1 in the word HEADING the letter A istypewritten on a line at a position immediately below that whereexemplary magnetic bits corresponding thereto are recorded, but therelative positions of the recorded visible and magnetic data along thewidth dimension of the sheet are aligned.

Therefore, the horizontal rows of alphanumeric data are parallel to, butoffset a fixed distance from, the rows of single tracks of magnetic dataon the magnetizable side of the recording medium. Each alphanumbericcharacter is also in a prescribed vertical relationship (typicallyaligned) with each group of eight magnetic bits which are uniquely codedto represent that particular character.

The eight bits of recorded data representing one typed character areillustrated in FIG. 2 as oval lines carrying arrow heads indicating thepolarity of the magnetism of the particular recorded bit; the bitpolarity is also indicated by the relative positions of the magneticnorth and south poles, N and S, on the left and right sides of theassociated oval lines. Hence, magnetic 1 bits are represented by thesemutually tangential oval lines having arrowheads pointing in theclockwise direction, as well as N and S on the left and right sidesthereof. Magnetic 0 bits are of the opposite magnetic polarity and arerepresented by three mutually tangential oval lines having arrow headspointing in the counterclockwise direction, as well as by magnetic polesS and N on the left and right sides, respectively, of the associatedoval lines. The first six magnetic bits of each eight bit group, FIG. 2,indicate which key on the typewriter keyboard is depressed while theseventh bit indicates if the shift lever is depressed while thecharacter is recorded (upper or lower case character). The last oreighth bit is used as a parity bit for error checking.

The parity check employed in such that an odd number of l and 0 bits isderived for each character. To illustrate, for lower case letters a, thefirst six bits may be 101001 while the seventh bit is a 1 bit toindicate that the shift lever was not activated and the eighth bit isalso a 1 ,bit to provide the desired parity check. Upper case letter Awould have the same first six bits as a, namely 10100], but the seventhbit is recorded as a 0 bit to indicate that the shift key was activatedon the keyboard and the last bit is recorded as 0 bit to provide therequired odd parity check. 4

MAGNETIC RECORDING GENERAL The eight magnetic bits for each key arecreated simultaneously on layer 22 by applying a corresponding number ofrapidly changing electrical currents to the alloted area on the layer.Each magnetic bit so formed includes a north pole N and a south pole Slaterally spaced from each other by a relatively small distance with theorientations of the poles along the width dimension of the paperindicating the code of the recorded character. Each magnetic bit centeris spaced from an adjacent bit center a distance sufficient to provideadequate separation between adjacent magnetized areas to obtain asufficiently well-defined voltage waveform to satisfy the particularsystem readback requirements. A single track of magnetic bit groups isformed on layer 22 in positional correspondence with a line ofcharacters on sheet 21. As' a result, a self-synchronized readingapparatus may be employed to readout the magnetic record.

With reference to FIGS. 4-7 of the drawings, there is illustrated oneembodiment of the instant recording apparatus for simultaneously writinga human readable and a magnetic record on the sheet 21 and the layer 22,respectively. The apparatus, FIG. 4, comprises a conventional electrictypewriter 26 with a full 50-key keyboard having upper and lower casecharacters, as well as a backspace key 27, a special erase key 28 forerasing magnetic data, a space bar 29, a carriage return key 30, and ashift key 31.

Erase key 28, space bar 29, carriage return key 30 and shift key 31 allhave permanent magnets 32 fixedly mounted on lower extensions thereof.Each of the magnets is movable past an associated reed switch 35 upondepression of its associated key or bar; the reed-like contacts of eachswitch closing in response to the movement of a magnet therepast.

Electrical signals produced upon reed switch closure indicate which ofthe erase key 28, space bar 29, carriage return key 30 or the shift key31 has been depressed by the typist. In addition to the special signalsderived in response to depression of keys 28, 30 and 31 and bar 29, asignal is similarly derived upon depression of any of the remaining keyson the typewriter keyboard.

In addition to these signals, all signals produced in response to thedepression of the remaining keys on keyboard, other than erase key 28,and the shift key 31 and fed to a diode coding matrix designatedgenerally by numeral 36 via a multi-lead cable 37. The electricalsignals fed to the matrix are obtained from closures of individualswitches, the state of which, as mentioned above, are under the controlof magnets associated with individual keys on the keyboard. Assumingthat the remaining keys total fifty, there will be 50 additionalswitches and 50 additional connecting leads. Matrix 36 is constructed sothat if any one of the 50 leads is connected to ground in response toclosure of an associated switch by activation of a selected key on thekeyboard, eight predetermined binary electrical signals aresimultaneously produced on eight conductors leading out of the matrix.The first six bits indicate which key of the keyboard has beendepressed, the seventh bit indicates whether the shift key 31 has beendepressed and the eighth bit is employed as a parity check. Specialcodes are associated with spacer bar 29 and carriage return key 30,whereby the binary bit combination for these keys is different from thatof any other keys, while preserving the parity check. To preserve theparity check for upper case characters, diode coding matrix 36 includesmeans for inverting the parity bit for each character in response toactivation of shift key 31, well as means for generating a bit as theseventh bit if the shift key 31 is activated. The eight predeterminedsignals obtained from the output of the diode coding matrix 36 areapplied to the recording circuit 39. High amplitude current pulsesgenerated at 39 pass thru the normally closed relay contacts of aswitching circuit 38 to recording head 41, fixedly mounted above aplaten 42 in typically horizontal alignment with a type guide 43. 1

With reference to FIGS. 1, and 6, a magnetic recording head 41 isfixedly mounted to an arm 45 having an enlarged inner end fixedlymounted on a hollow shaft 47 which in turn is mounted integral with theframe of the typewriter. With the head 41 fixedly positioned centrallyof the typewriter frame in typical alignment with the type guide 43. Theshaft 47, which carries the arm 46 and head 41, is typically on theorder of three times the length of the platen 42 in order to permit therecording of magnetic characters at either edge of the medium 21, 22.Signals from switch 38 are coupled to head 41 by conductors sheathed ina cable 48 and inserted into the shaft 47 and emerging from the interiorof the shaft and the arm 46 by way of a bore 46A extending transverselythrough a portion of the arm and the shaft. Each of the conductorsforming cable 48 is connected to one terminal pin of a standardmultiterminal connector plug 60, which is manually insertable intoconnector receptacle 59 of head 41, as indicated by FIGS. 1 and 5.

MAGNETIC RECORDING DETAILS OF RECORDING HEAD With general reference toFIG. 6, the head 41 is characterizable a coreless magnetic head havingthree sections AB and C; each equal in width, and typically 100 milswide, with each section performing a different function determined by aselected mode of typewriter operation. The first section designated A,comprises a plurality of turns, typically 52, of a single, continuousconductor having two end leads 49A and 498, respectively, which areenergized when it is required to erase (by degaussing) a previouslyrecorded character. During an erase mode, in section B, between sectionsA and C, a discrete magnetizable area of the backing 22 is erased beforea recording is made thereon, thereby ensuring a greater accuracy andintegrity to recording. To this end, fringe areas at both ends of recordsection B are degaussed by appropriately energizing spaced windingsseparating section B from sections A and C, respectively. Similarly,section A during the erase mode erases the discrete record area andadjacent fringe areas of a previously recorded character. The degaussingof fringe areas also reduces the possibility of nonerased, previouslyrecorded magnetic bits remaining on a reinserted, slightly misalignedpaper 21 in the typewriter. In section C-, adjoining section B, an areais similarly erased while a preceding character is recorded in sectionB. Section C is formed by a plurality of turns of a single, continuousconductor having lead ends 51A and 513, respectively.

Typically, each conductor is constituted by a copper wire having adiameter of 1.75 mils coated with an electrical insulating layer ofpolyurethane of 0.1 mil thickness. Each conductor is wound evenly arounda mandrel-like portion 52 of the head frame 41' so that an elongatedsection of each convolution is in physical contact with the layer 22.Because each section of conductor is coated with insulation, shortcircuiting is prevented between mutually adjacent conductors. Parts ofthe recording head 41 other than the conductors wound upon the portion52, are preferably composed of a suitable insulating material, such as apolymeric or epoxy resin.

For each magnetic bit recorded on the backing 22, only every fifthwinding or turn of section B (FIG. 6) is energized and the remainingfour windings or turns for that bit are utilized as spacers between theenergized windings. Eight single conductors are interleaved betweencertain juxtaposed but spaced-apart convolutions of the continuouswinding on the mandrel 52. Each such recording conductor forms less thana complete turn on the mandrel and typically has a portion of lengthsuitably affixed to only the top, bottom and from surfaces of themandrel as viewed in FIG. 6. Also, each recording conductor is separatedby four spaced turns which are merely spacers, and are not supplied withsignals. In FIG. 6, numerals 53-1 and 53-2 designate the recordingwindings for the first and second bits of a character, respectively, andthe spacer turns are designated 54. The seventh and eighth recordwindings are designated 53-7 and 53-8, respectively. Of course, it is tobe understood that the dimensions illustrated in FIG. 6 are greatlyexaggerated and that the total lateral distance between record winding53-1 for the first bit of a character and record winding 53-8 for thelast (eighth) bit of that character is typically on the order of 68mils. In the manner described for spacing windings 53-1 and 53-2 forrecording the first and second bits, four spacer conductors are utilizedto maintain precise separation between each of the six remaining recordwindings 53-3 53-8 from one another. Thus, section A is defined by thewindings connected to leads 49A and 49B, section B is defined by thewindings connected to leads 50A and 508, said section C is defined bythe windings connected to leads 51A and 518, with leads 49B, 50A and50B, 51A, respectively, being commonly connected at single terminals.Leads 498, 50A and 50B, 51A extend from a continuous winding, asdisclosed above, and recording lead pairs 53-1A, 53-1B 53-8A, 53-8B,extend from less than single complete turns of corresponding recordingwindings 53-1 53-8.

It may be noted that no magnetic core material is employed in the head41 and that turns having insulation thereon are utilized as spacersbetween adjacent recording turns. Sufficient magnetic flux is applied bywindings 53-1, 53-2 53-8 to magnetic backing 22 by pulsing these turnswith high intensity currents and by allowing these turns to contact thebacking 22. As described, infra, ciruitry is provided to pulse windings53-1, 53-2 53-8 with currents having peak magnitudes on the order of 20amperes for approximately microseconds. Such currents create enough fluxaround the windings to appropriately change the magnetic state of adefined, adjacent area of the layer 22. The extremely large amplitudecurrents do not overheat the conductors to the point to rupture becauseof the extremely short time duration of these pulses.

OTHER EMBODIMENTS OF THE RECORDING HEAD Section B of the head 41 may bemodified such that two separate adjacent windings are utilized forrecording each bit. In such a configuration, the current flowing througha first one of the two windings is in a direction opposite to thecurrent flowing through the second one of the two windings for the samebit, whereby the first winding is witched to a first current source whenthe particular bit is a binary l and the second winding is switched to asecond current source when a binary O is to be recorded. As in the caseof the FIG. 6 embodiment, the recording windings for each bit areseparated by four spacer windings to provide the desired fringe spacingson either side of each magnetic area commensuarate with the arearequired for a character.

FIG. 7 illustrates another embodiment of a recording head, designated41, wherein contact between backing 22 and a surface 58' of the head 41is maintained by a plurality of apertures 89 extending perpendicular tothe surface of the head that contacts backing 22. Apertures 89 areformed in the head 41 during the manufacture thereof and communicatewith a common bore 90 connected to a suitable source of fluid pressure,such as a vacuum pump (not shown). The pump applies a subatmosphericpressure of approximately 13 pounds per square inch to the backing 22 byway of the aperture 89, this vacuum being sufficient to maintain therecord medium in firm contact with the recording winding 53-1. 53-8, andis controlled by a solenoid valve 91-1, FIG. 1, installed in tube 91.Alternately, an above atomspheric pressure applied via tube 90, may becontrolled by an in-line solenoid valve installed in the tube 91.

According to still another embodiment of the invention, the longitudinalaxes of erase and recording windings are mutually orthogonal, that is,positioned at right angles to each other. In such case the erasewindings are located on character position on either side of theintermediate section B of FIG. 6 to enable erasing prior to recording orin response to depression of say a backspace key. Thus, the two erasewindings would be positioned orthogonal to the windings depicted insections A and C, respectively, in FIG. 6.

Another embodiment of the invention would place all of the record anderase conductors mutually parallel to each other and spaced onecharacter apart with their respective longitudinal axes aligned. Thus,the two erase windings and record windings would be positionedorthogonal to the windings depicted in sections A, C and B, respectivelyof FIG. 6.

A further embodiment would place the record conductors orthogonal to theerase conductors and one character apart from one another. Thus, therecord windings would be orthogonal to the record winding depicted insection B of FIG. 6.

The windings of the head 41 may be made in the form of thin, flatconductive strips (FIG. 8 and 8A) having a dimension Y perpendicular tothe plane of the backing 22 substantially greater than dimension X.Dimension X is proportioned to give a current density that is nearlyequal to its counter part wire conductor of FIG. 6.

All other factors being equal, the substantially greater amount of metalavailable in the strip-like windings provides a somewhat longer lifetimeof wear of the recording windingns. FIG. 8 illustrates one set ofidentical spacer strips -1, 952 corresponding to two of the spacerwindings 54in section B of FIG. 6 of the recording head prior toconnection in electrical series. The strip designated 96 depicts arecording strip corresponding to one of the recording windings 53-1 53.8of FIG. 6. Numeral 97 designates a strip corresponding to the firstwinding of the head to which the lead 49A is joined, FIG. 6. The strips98-1 and 98-N illustrate representative erase strips in section A of therecording head.

FIG. 8A depicts a typical electrical series connection of the variousspacer strips 95 to each other and to an adjacent strip 98-N as well asseries connection of the terminal strip 97 to a juxtaposed erase strip98-1. The strip 98-1 is electrically connected to the strip 97 whichreceives erase current pulses via the lead 49A. The edges and sides ofthe various strips may be coated with a layer of a suitable electricalinsulating material to prevent short circuits therebetween. The materialmay be a suitable epoxy compound which adheres to all surfaces of thestrips except the forwardmost edge of each strip leg which contacts thebacking 22. It will be noted that in order to interleave the recordingstrip 96 between two other strips such as the strips 95-1 and 98-N, thetwo parallel legs of each strip are bent in opposite directions out ofthe strip plane, FIG. 8 and passed between the bifurcated arms of thestrip 96. A physical and electrical connection is then made between therespective downwardly and upwarrdly extending end portions of the strips95-1 and 98-N. Connections are similarly effected between all juxtaposedstrips save the strips utilized for recording, such as the strip 96.

MAGNETIC RECORDING DETAILS OF TYPEWRITER MECHANISM To ensure that therecord windings designated 53-1, 53-2 53-8 are in virtual contact withthe magnetic surface of the layer 22 FIG. 5, the head 41 is placeddirectly above platen 42 and is contoured along the lower surface toconform closely with the cylindrical portion of platen 42 immediatelyabove the point where type bar 25 strikes the sheet 21.

To maintain the layer 22 is contact with conductors 53-1 53-8, platen 61is mounted on carriage assembly 50 approximately directly above platen42 and has its longitudinal axis extending parallel to the longitudinalaxis of the lower platen. Platens 42 and 61 carry radially-projectingpins 62 for engaging pinholes 63 lorection of the current pulse throughany one winding is dependent upon which of two circuit inputs isactivated. Since each stage is essentially identical to the other seven,a description of only the stage for the winding 53-1 suffices.

This stage, referred to as block 1 in FIG. 13, includes a pair of inputterminals 112 and 113 which are selectively connected to groundpotential at terminals 114 and 115 by operation of one of the switches116 and 117 which are respectively operatively associated with twodifferent type bar mechanisms on the typewriter. Switches 116 and 117,which may be of the electronic type are illustrated as being mechanicalswitches for ease of explanation of operation, it being understood thateach key on the typewriter keyboard has a single switch such as 116 or117 associated with it. If the first bit in a character being recordedis a 1 bit, switch 117 is driven from its normally open state to aclosed state upon pivoting of its associated type bar mechanism, therebyplacing ground on one coordinate of the diode matrix 36. This cause thematrix to generate eight binary coded output pulses which activatedifferent control devices in the stages 1 8 inclusive. The binary outputsignals of the matrix 36 are uniquely coded to represent eachalphanumeric typewriter key. The stages 1 8, inclusive, thereby convertthe binary output of the matrix into corresponding directionallycodedrecording currents. Switch 116 remains open during closure of switch 117since its associated key is not depressed during this type interval.Switch 117 remains closed until its associated type bar mechanism, inits return movement, travels a predetermined distance from the paper orplaten whereupon the switch reopens. Thus, only one switch, such as 117is closed at any one time.

Terminals 112 and 113 are connected through matrix didoes 118-1M and119-1M, coupling diodes 118 and 119 as well as resistors 120 and 121, tothe gate electrodes of silicon-controlled rectifiers 122 and 123,respectively. The gate electrode of silicon-controlled rectifier (SCR)122 is connected to the reference 6 volt potential at terminal 124through a resistor 125. The gate electrode of SCR 123 is connected tocontact 1018 at one side of winding 53-1 through a resistor 126. Theother contact 101A formed on the other side of winding 53-1 is connectedto the reference voltage at terminal 124 through 0.2 ohm resistor 127,such resistor being utilized to monitor the current through winding53-1. Hence, when the system is in a quiescent condition and switches116 and 117 are both open, resisors 125 and 126 apply approximately a 6volt DC. potential to the gate electrodes of SCRs 122 and 123,respectively, to maintain these rectifiers in a cutoff condition.

Under quiescent conditions, the anodes of siliconcontrolled rectifiers122 and 123 are connected to a +B3 volt D.C. supply at terminal 128 viathe path through contact 129 of relay 130, and the parallel pathsthrough hold-off diodes 132 and 133, which are respectively connected inseries with resistors 134 and 135. The cathode of silicon-controlledrectifier 122 is connected to the 6 volt DC potential at terminal 124.Resistor 127 and winding 53-1 have an extremely small series impedanceand since there is no current flowing, except a small leakage current,there is very little voltage drop, and therefore, the cathode electrodeof SCR 123 is also maintained at approximately 6 volts DC. atquiescence.

Bipolar high ampere pulses may also be fed through winding 53-1. Asillustrated, the andoes of SCRs 122 and 123 are respectively connectedto one electrode of each of capacitors 137 and 138. The other electrodeof capacitor 137 is connected to contact 1018, resistor 126 and theanode of SCR 123 while capacitor 138 is connected directly to the 6 voltD.C. source at terminal 124. Current derived from the initial charge oncapacitor 137 passes thru winding 53-1 with the current flowing fromleft to right, FIG. 13, in response to SCR 122 being rendered in aclosed circuit condition while current flows in the opposite directionthrough winding 53-1 in response to current derived from capacitor 138when the anode-cathode path of SCR 123 is closed. Current flow from leftto right typically corresponds to the recording of a 0 bit whereascurrent flow from right to left typically corresponds to the recordingof a 1 bit.

Normally closed contact arm 129 couples the positive DC. voltage atterminal 128 to capacitors 137 and 138 during the interval when no keyon the keyboard is activated. Contact arm 129 is open circuited duringvirtually the entire interval when a key on keyboard is depressed inresponse to activation of relay coil whereby the current supplied bycapacitors 137 and 138 to winding 53-1 is of predetermined duration.Relay coil 130 is connected in the collector circuit of NPN powertransistor 139 and is shunted by reverse biased protecting diode 141.The emitter of transistor 139 is connected directly to the negativevoltage at terminal 124. The base of transistor 139 is connected to thenegative supply at terminal 124 through resistor 142 and is connected toterminals 112 and 113 through isolating diodes 144 and 145 and matrixdiodes 118-1M and 119-1M respectively.

Under normal operating conditions, transistor 139 is maintained in anon-conducting condition by the negative voltage applied to its basethrough resistor 142 thereby causing the base and emitter to be at thesame voltage level. With transistor 139 non-conducting, contact arm 129is closed, whereby capacitors 137 and 138 are fully charged throughcomponents 132, 134 and respectively to a potential of, for example, +35volts. The charge is maintained on capacitors 137 and 138 underquiescent conditions because the anodecathode paths of SCRs 122 and 123are cut-off. In response to a depression of a key on the keyboard one ofswitches 116 and 117 is closed to apply a forward bias to the base of apower transistor 139. Forward biasing transistor 139 causes relay 130 bobe energized, opening contact arm 129.

The triggering of eighth SCR 122 or 124, however, occurs before thecontact arm 129 opens because the response of the relay 130 issubstantially slower than that of the SCRs. In response to closing oneof contacts 116 or 117, the charge on one of the capacitors 137 or 138is immediately conducted through the anodecathode path of the SCR havingits gate electrode connected to the closed switch. Capacitors C and Care sufficiently large, having a magnitude of 12 microfarads, and theforward impedance of SCRs 122 and 123, is low enough so that a currentpulse having the required amplitude andduration is produced. Because ofthe extremely low impedance in the resistancecapacitance circuitconnecting winding 53-1 to the selected one of capacitors 137 or 138,virtually all of the

1. The combination of a typewriter apparatus having a plurality oftypewriter keys and a magnetic recording system for recording magneticbits on a magnetizable medium mounted on the typewriter platen, therecording system comprising a plurality of stages for producinghigh-ampereage currents, the flow directions of certain currents beingdifferent and coded to represent different ones of the typewriter keys,each of said stages including a first and a second control device havingat least one control electrode, an output electrode and a thirdelectrode, first and second capacitors under the control of saiddevices, the first capacitor coupling the output electrode of saidsecond device to the third electrode of said first device and the secondcapacitor coupling the output electrode of said first device to thethird electrode of said second device, means for charging saidcapacitors prior to actuation of a typewriter key, means coupled to thecontrol electrodes of said devices and responsive to actuation of atypewriter key for activating one said devices, whereby one of saidcapacitors discharges current through the output electrode of the onedevice, and a conductor associated with each of said stages mountedadjacent said platen and said medium and connected to the one outputelectrode for inducing a magnetic flux in said magnetic medium ofpolarity determined by the direction of current flow in said conductor.2. The combination as claimed in claim 1 which additionally comprises,means for selectively deactivating said control devices of all saidstages to prevent magnetization of said medium upon activation ofcertain of the typewriter keys.
 3. The combination as claimed by claim 2which additionally comprises, means activated by a shift key on thetypewriter for generating a predetermined current flow in one of saidconductors of a change from lower to upper case.
 4. The combination of atypewriter apparatus having a plurality of keys and a system forrecording an erasing discrete magnetized areas on a magnetizable mediummounted in the typewriter apparatus comprising, a recording head havinga plurality of parallel juxtaposed conductors facing said medium inadjacency therewith, first means for generating current flows to certainones of said conductors upon actuation of a selected key in directionswhich represent such key whereby a first discrete area of the medium ismagnetized by induction from the currents, and second means responsiveto actuation of said selected key for generating current flows in otherones of said conductors to magnetically erase a second discrete area ofthe medium contiguous to the first area and in the direction of mediummovement in the typewriter.
 5. The combination as claimed in claim 4wherein said other ones of saiD conductors are interleaved with saidcertain ones of said conductors and wherein said selected key is a backspace key, whereby activation of said backspace key erases and areaprior to recording thereon.
 6. The combination as claimed in claim 4wherein the other ones of said conductors are positioned on each side ofsaid certain ones of said conductors to effect erasure of areas fringingsaid first discrete area, and means coupling the second generating meansto all of said other ones of said conductors.
 7. The combination asclaimed in claim 4 which further comprises means for selectivelyapplying the second generating means to said certain ones of saidconductors.